Ammonia, volatile alkali. The origin of the word is uncertain; some authors suppose it to be from the god Amnion, near whose temple in Upper Egypt it was produced; others from Ammonia, a Cyrcnaic territory; while others again derive the word from sand, because the sal ammoniac was found in the sands of Africa. Pliny was probably acquainted with it; it was afterward discovered in 1677 by Kunckel, still later in 1756 by Dr. Black, and finally more fully described by Dr. Priestley in 1774. It is composed of one volume of nitrogen and three volumes of hydrogen, which on combination condense to two volumes. In its pure state, and at the ordinary temperature and pressure, it is a colorless, pungent gas, wholly irrespirable, not a supporter of combustion, excepting of bodies which readily combine with hydrogen, strongly alkaline, having a specific gravity of 0.59, and readily converted into a liquid by cold or pressure. The elastic force of the vapor of liquid ammonia at different temperatures, according to Bunsen, is as follows: at - 33.7° C. = 1 atmosphere; at - 5° C. =4 atmospheres; at 0° C. =4.8; at +5° C. =5.6; at +10° C. = 6.5; at +15° C. = 7.6; at +20° C. = 8.8. Bunsen prepared the liquified ammonia by causing the perfectly dry gas to pass through a column of hydrate of potash, and thence into a tube cooled to - 40° C. The liquid ammonia is colorless, very mobile, having a specific gravity of 0.63. It freezes under a pressure of 20 atmospheres at - 75° C, and at - 87° C. in vacuo.
This solid, frozen ammonia is a white, transparent, and crystalline body, possessed of a faint odor. Liquid ammonia is a powerful solvent for a number of metals, as has been recently (1871) shown by Professor Charles A. Seely of New York. Two important applications of liquid ammonia have been made in modern times. The first is its employment as a motive power according to the invention of a French chemist, M. Tellier; and the second is the invention of M. Carre to use it for the artificial production of cold. One gramme of water at 0° C. and 760 mm. pressure absorbs 0.877 gramme or 1,149 times its volume of ammonia gas; at 20° C. it absorbs 681 times its volume and yields the liquid ammonia of the shops. - Commercial ammonia was formerly obtained from the sal ammoniac of Africa; but this source is entirely inadequate to supply the present demand, and recourse has been had to numerous other sources. The greater part of the aqua ammonias of the shops is derived from the waste liquors of the manufactories of illuminating gas. The ammonia of the boracic acid works of Italy is also saved, and some establishments yield 3,300 lbs. of sulphate of ammonia every 24 hours, in addition to the boracic acid which is condensed in the water.
Some of the crude crystals of borax contain nearly 4 per cent, of ammonia, and when these are fused with soda, the ammonia is driven out and can be condensed in suitable vessels. When caustic soda is mixed with Chili saltpetre, much ammonia is liberated, which can be condensed and saved. The ammonia arising from the beet in the manufacture of sugar and from the gas in coking furnaces is also economized to some extent. The preparation of ammonia for the arts is founded upon the action of quicklime upon a convenient ammoniacal salt. It is customary to distil an intimate mixture of one part of pulverized sal ammoniac with two parts of moistened lime, and to condense the gas in water. On a large scale ammonia is obtained directly from gas-house liquors, without being previously converted into sal ammoniac. - Ammonia is produced in the juices of various nitrogenous animal and vegetable substances in their putrefactive fermentation. It is given out in their decay, and, passing into the atmosphere, is condensed by the aqueous vapor, and returned to the earth in rain water, mists, and snow. It furnishes to plants the nitrogen they require, and is thus the principal valuable ingredient of the manures. Guano is a great repository of it.
The shavings of horn have been used to prepare it, whence the name spirits of hartshorn. It is given out in the destructive distillation of all bituminous mineral matters, coming over in an impure state, condensed in the aqueous vapors, and mixed with the tarry products. This is the source from which it is now principally obtained for commercial purposes. It is also evolved from urine in a state of decomposition; and from this substance are prepared annually in Paris from 17,000 to 18,000 lbs. of ammoniacal salts. Refuse animal substances, as bones and horns, blood and hair, horse flesh, and rags of wool and silk, are made to yield a variety of ammoniacal salts - as the carbonate and acetate - by distilling them. The chief product is the subearbonate of am-monia in solution. From the solid matters that will not distil over are obtained animal black, which is used for clarifying sugars, and a carbonaceous substance employed in the manufacture of Prussian blue. Sal ammoniac is pre-pared from the crude carbonate thus obtained in combination with the ammoniacal products of the gas works and other operations referred to The liquors are saturated with muriatic acid and evaporated; the salt deposited is dried and then sublimed, by which means it is collected free from impurities.
Am-monia yields numerous salts, some of which are employed in the arts. They are all readily destroyed by heat. - The water of ammonia, the carbonate, chloride, and acetate, are used in medicine; the first externally as an irritant or to develop the gas; the others internally. Their effect is to temporarily accelerate the heart's movements, by an action rather on the muscular than on the nervous apparatus, and to liquefy mucus where they come in contact with it, either directly as in the stomach and intestines, or in the way of elimination, as in the bronchial tubes. It leaves the system by the lungs, skin, and kidneys, having much less effect than the fixed alkalies in alkalizing the secretion of the latter organ. Carbonate of ammonia is used as a rapidly diffusible stimulant in various diseases, especially febrile and neuralgic, and sometimes as an expectorant, its action being twofold, strengthening the bronchial muscles and liquefying the mucus. The chloride, though it is less powerful as a stimulant, is used for similar purposes, and also in some affections of the digestive organs. The liquor ammoniae acetatis or spiritus Mindereri is, in the doses usually given, but little more than a placebo.
Ammonia, in the gaseous or liquid form, has been proposed as an antidote to several poisons, especially alcohol, carbonic acid, and prussic acid. For these purposes the stimulant action is desired, but the gas must be used with great caution on account of its irritant effect on the air passages. The injection of ammonia into the veins, as a cure for the bite of venomous serpents, has been practised by Prof. Halford of Australia, and others on his recommendation. Although recoveries have been reported, the question of its efficacy must be regarded as still unsettled.